type get_state =
  | GLUT_WINDOW_X
  | GLUT_WINDOW_Y
  | GLUT_WINDOW_WIDTH
  | GLUT_WINDOW_HEIGHT
  | GLUT_WINDOW_BUFFER_SIZE
  | GLUT_WINDOW_STENCIL_SIZE
  | GLUT_WINDOW_DEPTH_SIZE
  | GLUT_WINDOW_RED_SIZE
  | GLUT_WINDOW_GREEN_SIZE
  | GLUT_WINDOW_BLUE_SIZE
  | GLUT_WINDOW_ALPHA_SIZE
  | GLUT_WINDOW_ACCUM_RED_SIZE
  | GLUT_WINDOW_ACCUM_GREEN_SIZE
  | GLUT_WINDOW_ACCUM_BLUE_SIZE
  | GLUT_WINDOW_ACCUM_ALPHA_SIZE
  | GLUT_WINDOW_DOUBLEBUFFER
  | GLUT_WINDOW_RGBA
  | GLUT_WINDOW_PARENT
  | GLUT_WINDOW_NUM_CHILDREN
  | GLUT_WINDOW_COLORMAP_SIZE
  | GLUT_WINDOW_NUM_SAMPLES
  | GLUT_WINDOW_STEREO
  | GLUT_WINDOW_CURSOR
  | GLUT_SCREEN_WIDTH
  | GLUT_SCREEN_HEIGHT
  | GLUT_SCREEN_WIDTH_MM
  | GLUT_SCREEN_HEIGHT_MM
  | GLUT_MENU_NUM_ITEMS
  | GLUT_DISPLAY_MODE_POSSIBLE
  | GLUT_INIT_DISPLAY_MODE
  | GLUT_INIT_WINDOW_X
  | GLUT_INIT_WINDOW_Y
  | GLUT_INIT_WINDOW_WIDTH
  | GLUT_INIT_WINDOW_HEIGHT
  | GLUT_ELAPSED_TIME
